GC-IR hyphenated technology combines the separation power of gas chromatography and the molecular identification power of FTIR, and provides a single-instrument configuration to obtain molecular vibrational spectra of each analyte as it emerges from the GC separation of multi-component complex samples. GC-IR automatically generates solid-phase IR spectra for each peak which  can be compared to the various IR libraries. GC-IR is particularly useful to identify isomers having similar MS at low ng sensitivity. Analysis of Fatty Acid Methyl Esters (FAMEs) is an important tool to characterize fats & oils and to determine total fat and trans-fat content in foods. The GC-IR spectra of each FAME peak yield information about the chain length, the degree of unsaturation and cis/trans isomers. The FAME chain length can be determined from the IR peak height ratio of CH2 (~ 2920 cm-1) and C=O (~1740 cm-1) groups. For the FAME peaks derived from unsaturated fatty acids, the IR spectra showed the appearance of the olefinic CH peak just above 3000 cm-1 and the downward shift of the ester peak from near 1740 to 1731 cm-1 with a unique 965 cm-1 peak for trans isomers. Various examples will be presented to illustrate the GC-IR capability in characterizing FAME samples including the complete de-formulation of a 37-component FMEA mixture.The IR spectrum provides specific information about the local bonding environment in a molecule, and many functional groups have been correlated with specific IR bands. GC-IR hyphenated technology can be a useful tool to identify and classify unknowns, and characterize very similar structural isomers from various natural products such as foods, plant oils, fragrances, flavors, herbs after the GC separation of their extract mixtures.

Characterizing fatty acid methyl esters and natural products by GC-IR hyphenated technology

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.